Induction-preventive for telephones



(No Model.)

T. F. WRIGHT & E. G. WILSON.

INDUGTION PREVENTIVE FOR TELEPHONES. N0.447,858. Patented Mar. 10,1891.

W :by (5M UNITED STATES PATENT OFFICE- I THOMAS F. VRIGHT AND ED. GWILSON, OF CHICAGO, ILLINOIS.

lNDUCTION-PREVENTVE FOR TELEPHONE S.

SPECIEICATION formng part of Letters Patent No. 447,858, dated March 10,1891.

Application filed July 28, 1890.

:seria No. 880.165.V (No model.)

T all whom, it may conccrn:

Be it known that we, THOMAS F. WRIGHT and ED. G. WILSON, both ofChicago, county of Cook, and State of Illinois, have invented certainnew and useful Improvements in Induction-Preventives for Telephones, ofwhich the following is a specification.

This invention relates to improvements in induction preventives fortelephones, but more especially to that class in which the device isattached to the receiver.

Prior to this invention numerous devices have been invented forpreventing` induction in telephones, but so far as we are aware none ofsuch devices have been practically successful When subjected to theordinary conditions under which they must operate; but our invention hasbeen practically tested under all the usual ,conditions and proved bothoperative and successful, the prime object thereof being to preventinduction without materially or injuriously reducing` the strength ofthe talking-current.

Another object is to have the device of such a character that it isreadily attachable to and adapted for use in connection with theordinary hand phones or receivers now in use.

These objects are attained by the devices illustrated in theaccompanying drawings, in which- Figure 1 represents a side elevation ofan ordinary telephone-receiver of the Bell pattern, having an inductiondevice Aapplied thereto embodying my invention; Fig. 2, a centrallongitudinal section thereof; Fig. 3, a face view of the inductiondevice detached from the receiver, and Fig. 4 a side elevation thereof.

Similar letters of reference indicate the same parts in the severalfigures of the drawmgs.

Referring by letter to the accompanying drawings, A indicates a casingpreferably composed of sheet metal, having the external appearance of asmall cup or bowl, of such di-- mensions and contour as to fit snuglywithin the concavity or depression in the end of the receiver, as moreclearlyillustrated in Fig. 2, the face or interior portion of thecasing, however, having preferably an irregular Shape, being concavedaround the outer portion or cdges of the cup and provided with a centrala projecting portion or dome B, intended to fit against and within thecar, which latter Will be practically covered by the casing when appliedthereto. The two walls of the casingthat is, the front andbackthereof-are provided with central perforations C D, between which apractically-continuous passage is formed by the insertion of a tube E ofany suitable material, but which is, preferably, composed of a coil ofsmall steel Wire, which in practice has proven to produce the mostdesirable results, although we are not pre= pared to state that otherforms of tubes and other material cannot be employed With equally goodresults. Surrounding this tube, but inclosed within the casing, is aspool F, preferably of Wood, of any suitable shape or dimensions, themost desirable being that conforming to the interior of the casing. Thisspool is grooved externally, asshown, and has wound thereon a coilof`fine wire G, copper being found to produce the desired results, oneend of which H is inserted or driven into the spool, while the other andfree end I terminates immediately in front of, but pref-- erably out ofcontact with, the diaphragm J of the telephone-receiver, which lattermay, if desired, be perforated at the center immediately opposite theterminal of the coil, as shown at K, which we have found in someinstances to promote the effectiveness of the device, while in othersthe perforation could be dispensed with,son1etimes without changing andsometimes promoting the results.

This induction device may be attached to the receiver in any suitablemanner either by the spring-hook L, attached to the casing A, engagingthe usual fiange upon the end of the receiver, or by any other devicewhich will accomplish the desired result.

In practice we have found it most desirable, if not essential, that theWooden spool F be kept at all times in a perfectly-dry condition, and tothis end We have usually dipped the spool in melted paraffiue after thecoil has been wound thereon, thus effectually insulating the sameagainst dampness; but other means may be employed for accomplishing thesame end without departing' from the spirit of this invention.

It has also been our practice to have the wire forrning,` the coil Gcovered with an in'- sulating-wrapping of some kind, so as toelectrieally insulate the coils froln each other and from the' casing,the extreme free ends H and I only being exposed or without insulation.

So far as we are aware the shape'or the di- Inensions of the casiug, aswell as of the core, is immaterial, and may be made of any suitable formand size best adapted for the intended uses, nor is it absolutelyessential that the spool surround the tube or that the coil be Woundupon a'spool, so long as the inner end H thereof is embedded in orother- Wise connected with a block of Wood or other equivalent for thecoil, the arrangement herein shown, however, being the most advantageousand convenient known to us, nor are we prepared to state the theory ofoperation of this device, but simply that it does operate to `absolutelyprevent induction under all ordinary conditions, and that itsoperativeness has been practieally tested and demonstrated.

Having described our invention, What we claiin, and desire to secure byLetters Patent, 18-- 1. An induction-preveutive for telephones,comprising a hollow casing having perforations therein, a tubeextending' between said perforations, and a coil one end of which iselnbedded in a spool or block of wood or its equivalent and the otherterminates opposite the center of a perfo-ration in the casing opposingthe diaphragrn of a telephone-receiver to which the casing is secnred,substantially as described.

2. An induction-preventive for telephones7 comprising a hollow easingprovided with perforations, a tube consisting of a coil of metallic Wireextending between said perforations, and a coil one end of which isembedded in a spool or block of Wood or its equivalent and the otherterminates opposite the center of a perforation in the easing opposlngthe diaphragxn of a telephone-receiver to which the casing is secured,substantially as -ing, and a coil of Wire wound upon said spool,

one end of which is embedded in the spool and the other terminatesopposite the center of a perforation in the easing' opposing thediaphragm of the receiver to which the device is secured, substantiallyas described.

4. An induetion-preventive for telephones, comprising a hollow casingprovided with perforations, a tube consisting of a coil of metallic wireextending between said perforations, a spool located within said casing,and a metallic coil Wound thereon, one end of which is embedded in thespool and the other end terminates opposite the center of theperforation in the casing opposing the diaph ragm of thetelephone-receiver to which the device is secured, snbstantially asdescribed.

5. The combination, with a telephone-receiver and the diaphragm thereofprovided with a central perforation, of an induetionpreventivecomprising a hollow casing provided with perforations, a tube extendingbetween said'perforations, a spoollocated within said casing, and ametallic coil wou'nd upon said spool, one end of which is embedded inthe spool and theother terminates opposite the center of the perforationin said diaphragm, substantially as described.

THOMAS F. WVRIGHT. ED. G. WILSON. Witnesses: I

R. O. OMoHUNDRo, A. MILO BENNETT.

